Glossary

RATHOLEA hole in the drilling floor in which the kelly joint is kept when not in use.

RECOVERABLE OIL An estimated measure of the total amount of oil which could be brought to the surface from a given reservoir.

RECOVERY FACTORThe ratio between the volumes of oil and /or gas produced and produceable from a reservoir and the oil and/or gas originally in place.

RE ENTRYInserting the drilling, testing or logging string etc. into the wellhead.

RESERVES/RECOVERABLE RESERVESOil or gas that it is anticipated can be produced. Technical Reserves are theoretically producible at a gross operating margin by e.g. normal primary or secondary recovery methods, while Commercial Reserves are restricted to volumes recoverable at an acceptable profitability. The detailed definitions are important in oil and gas financial and other information.

RESERVOIRA porous, fractured or cavitied rock formation with a geological seal forming a trap for producible hydrocarbons. A common exploration maxim is that a prospective target must possess a related Source rock, Structure and Seal.

RESERVOIR PRESSUREThe pressure at reservoir depth in a shut-in well.

REWORKING A WELLMaintenance work on a well to stimulate production. This may involve cleaning out silt deposits etc., or stimulation techniques such as fracturing or acidising.

RIGA collective term to describe the permanent equipment needed to drill a well. It has come to include the onshore and offshore vehicles, mobile platforms, or vessels on which the equipment is installed.

RIGGING UP Act of getting a rig assembled and ready to start drilling.

ROLLER BITA rotary drilling bit which penetrates by pulverising the rock with its toothed wheels.

ROTARY DRILLING Method of drilling in which the drill pipe is rotated in order to rotate a bit.

ROTARY TABLEThe heavy turntable at the centre of a drilling-rig floor, which is rotated by the main rig power supply, and in turn rotated by the kelly.

ROUND TRIPRecovering the drill string from the bottom of the well to the surface and returning it to continue drilling. This may be e.g. to replace the bit. "Tripping" is arduous and interrupts "making hole".

SEALSee Reservoir. An impermeable fault or stratum of rock beneath or behind which hydrocarbons can accumulate.

SECONDARY POROSITYPorosity developed after the original deposition of a formation, for instance by the action of water on soluble components of the rock or well stimulation techniques.

SEISMIC ACQUISITION (2-D, 3-D, 4-D) Seismic data are used to map subsurface formations. A 2-D survey reveals a cross section of the subsurface. In a 3-D survey, seismic data are collected in the inline and crossline directions to create a three-dimensional image of the subsurface. In a 4-D or time-lapse 3-D survey, 3-D surveys are repeated over time to track fluid movement in the reservoir.

SEPARATORA process vessel used to separate gases and various liquids in a hydrocarbon stream. A Wellhead Separator is the first process vessel in a production operation, operating at or near wellhead pressures.

SET CASINGInstallation of steel pipe or casing in a well bore, normally cemented in place by surrounding it with a wall of cement.

SHOEThe strengthened fitting on the lower end of a string of casing to protect the tubulars and help direct the cement to the annulus.

SHOWEvidence of hydrocarbons in a formation such as fluorescence in cuttings or gas in the mud returning from down hole.

SHUT-IT PRESSUREThe pressure in a shut-in well; static pressure.

SIDE-TRACK/SIDE-TRACKED WELLA well re-drilled from an intermediate depth. Wells are re-directed or sidetracked for various reasons, but usually because of technical problems deeper in the original well.

SIDEWALL CORINGObtaining rock samples from the sides of a well bore using a special tool.

SOLUTION GASSee Associated Gas

SPACING The distance between wells producing from the same reservoir. Spacing is often expressed in terms of acres, e.g., 40-acre spacing, and is often established by regulatory agencies.

SPUDTo start drilling a new well (or re-start)

SQUEEZEInserting cement under pressure into the poorly sealed annulus of a well, past the existing material.

STAND OF PIPEA short length of drill pipe pre-assembled to save time in operations and stored vertically in the derrick ready for use, usually in lengths of three joints.

STEP-OUT WELL Well drilled adjacent or near to proven well to ascertain the limits of the reservoir.

STICKINGJamming of the drill string in the well borehole caused by usually a high differential pressure and a build-up of mud solids on the rock face.

STRADDLE PACKERA rubber packer or seal isolating a section of a well for production testing of the formation in question.

STRATIGRAPHIC TRAP Subsurface formation created by sedimentation that might trap an accumulation of oil and/or gas.

STRINGSee Joint, Drill-string, Casing, etc. Any number of connected joints of tubulars run in the well.

STRUCTUREA geological formation which, if sealed against leakage, could be a potential structural or stratigraphic trap or hydrocarbons. A man-made load-bearing construction, such as an offshore platform, usually designed by structural engineers.

STUCK PIPEDrill pipe, casing, or tubing that cannot be worked in or out of the hole as desired.

SURFACE CASING First string of casing set in well.

SUSPENDED WELLA well, usually a successful discovery well which is left temporarily sealed or plugged to be re-entered for further testing or for production purposes.

SWABBINGOperation using a swab to bring well fluids to the surface when the well does not flow naturally.